How do I get a bad smell out of a car?

A car is a small sealed box with a lot of fabric in it, so any smell that gets in stays in. The two sources people miss are the underlay beneath the carpet and the evaporator behind the dashboard.

Safety

What you'll need

• A vacuum
• Enzyme cleaner for organic smells
• A new pollen filter
• An air conditioning cleaner (optional)
• Bicarbonate of soda (optional)

Step by step

1. Identify the type of smell.Damp and musty, sour milk or food, smoke, animal, or chemical. Each has a different source and a different treatment, and guessing wastes an afternoon.
2. Rule out the mechanical smells first.Petrol, burning, exhaust or a sweet syrupy smell mean a fault, not a cleaning problem. Get the car checked before doing anything else.
3. Empty the car completely and check under everything.Under seats, in the seat rails, in the boot well, under the spare wheel. Spilt milk, forgotten food and wet sports kit are found here more often than anywhere else.
4. Check whether the carpet is damp.Press a hand firmly into the footwells and the boot floor. Damp carpet is the most common cause of a musty car and it needs the leak found, not just drying.
5. Treat organic spills with an enzyme cleaner.Milk, food, vomit and animal accidents are protein-based, and enzyme cleaners break down the residue rather than covering it. Ordinary detergent leaves the source in place.
6. Deal with the air conditioning if the smell arrives with the fan.A musty smell that appears a few seconds after switching the fan or air conditioning on is bacteria on the evaporator, behind the dashboard. Nothing you clean inside the cabin will touch it.
7. Replace the pollen filter.Often behind the glovebox and a five-minute job. A filter that has been in for years is damp, dusty and part of the problem.
8. Use an air conditioning cleaner through the intake.Aerosol treatments are fed into the fresh air intake or the footwell vents with the fan running. It reaches the evaporator, which you cannot.
9. Shampoo or extract the carpets and seats.For a smell held in fabric, surface cleaning is not enough. A hot water extractor, hired or borrowed, pulls the source out rather than diluting it.
10. Dry the car thoroughly afterwards.Doors open in the sun, or a dehumidifier in a garage, or a long drive with the air conditioning running and the windows slightly open.
11. Absorb what is left rather than masking it.An open tub of bicarbonate of soda, activated charcoal bags or a bowl of coffee grounds left in the car for a few days absorbs residual smell. An air freshener does not.
12. Ventilate properly and often.Ten minutes with all the doors open does more than any product. Cars that are never aired develop smells that cars used with the windows down do not.

Tips

• Smoke smell is the hardest of all. It permeates the headlining and the ventilation ducts, and it usually needs professional ozone treatment.
• Do not put a scented product in until the source is gone. Two smells combined are worse than one.
• Damp in the boot is often a rear light seal or a tailgate drain rather than anything dramatic.

Common mistakes

• Hanging an air freshener and hoping — It adds a second smell on top of the first. The underlying source keeps producing, so the car ends up smelling of both.
• Cleaning only what you can see — Most persistent car smells live in the foam under the seat cover, the underlay beneath the carpet, or on the evaporator behind the dashboard. Surface cleaning cannot reach any of them.

If it doesn't work

Questions people ask